diff --git a/NOTES.md b/NOTES.md
index c17f940dbf57a0e339368800c7924f911a89ce10..536d4a0d020a615ba93589e6e82f1e1d0cf37e2f 100644
--- a/NOTES.md
+++ b/NOTES.md
@@ -9,6 +9,9 @@ Look up how godoc does references to other things.
 Figure out readline completion.  Case sensitive - issue?  Building from
 repl.commands?
 
+Switch between MAIL and BULLETIN modes? MAIL commands are documented
+[here](https://marc.vos.net/books/vms/help/mail/).
+
  ## sqlite
  
   * sqlite trigger tracing: `.trace stdout --row --profile --stmt --expanded --plain --close`